Blood disorders such as thrombocytopenia and anemia affect a significant population, with anemia being the most common disorder of the two. At least 50% of new patients admitted to a hospital's intensive care unit will develop thrombocytopenia during their stay. The development of thrombocytopenia correlates with mortality, longer duration of mechanical ventilation, and an increased need for blood product transfusion.
Anemia occurs when the level of healthy red blood cells (RBCs) in the body becomes too low. RBCs contain hemoglobin, which carries oxygen to the body's tissues. Thus, low levels of healthy RBCs can cause a variety of complications, including fatigue and stress on bodily organs. More than 3 million people in the United States have anemia. Women and people with chronic diseases are at the greatest risk for anemia. A person presents with anemia when the body loses too much blood (such as with heavy periods, certain diseases, and trauma); or the body has problems making red blood cells; or red blood cells break down or die faster than the body can replace them with new ones; or more than one of these problems happen at the same time.
Aplastic anemia occurs when the bone marrow cannot make enough RBCs. This can be due to a viral infection, or exposure to certain toxic chemicals, radiation, or medications (such as antibiotics, antiseizure drugs, or cancer treatments). Some childhood cancers can also cause aplastic anemia, as can certain chronic diseases that affect the ability of the bone marrow to make blood cells. Vitamin B12 and iron deficiencies also contribute to anemia.
Thrombocytopenia is a deficiency of platelets (thrombocytes). The blood usually contains about 140,000 to 440,000 platelets per microliter. Bleeding can occur with relatively minor trauma when the platelet count falls below about 50,000 platelets per microliter of blood. The most serious risk of bleeding, however, generally does not occur until the platelet count falls below 10,000 to 20,000 platelets per microliter. At these very low levels, bleeding may occur without any injury.
Abnormal reductions in the number of platelets are caused when abnormalities occur in any of the following three processes: decreased platelet production by the bone marrow; increased trapping of platelets by the spleen; or a more rapid than normal destruction of platelets. Persons with this condition easily bruise and can have episodes of excess bleeding (a hemorrhage).
Many diseases can cause thrombocytopenia. Thrombocytopenia can occur when the bone marrow does not produce enough platelets, as happens in leukemia, lymphoma and some anemias—aplastic, megaloblastic, vitamin B12 deficiency, and folic acid deficiency. Excessive alcohol consumption can also impede platelet production. Infection with the human immunodeficiency virus (HIV), the virus that causes AIDS, often results in thrombocytopenia. Platelets can become entrapped in an enlarged spleen, as happens in myelofibrosis and Gaucher's disease, reducing the number of platelets in the bloodstream. Massive blood transfusions can dilute the concentration of platelets in the blood. Finally, the body may use or destroy too many platelets, as occurs in many disorders, three of the most notable being idiopathic thrombocytopenic purpura, thrombotic thrombocytopenic purpura, and hemolytic-uremic syndrome.
Currently, the treatment options for anemia and thrombocytopenia are directed at the immediate increase of circulating RBC and platelet respectively, followed by identifying the underlying causes. Alternative treatment methods aimed at boosting the innate production of RBCs and platelets, for example, the use of erythropoietin and thrombopoietin to stimulate the bone marrow to produce more red blood cells, are still needed and will be useful in complementing existing treatments for anemia and thrombocytopenia.